• Geotechnical Engineering
• /
• v.9 no.2
• /
• pp.41-54
• /
• 1993

This paper presents the two and three -dimensional stability analysis of nonhom- ogeneous, c-o soil slopes. Potential failure surface is assumed as a logspiral curve refracted in boundaries of layers. In 3-D analysis, rotational soil mass is assumed with a cylindroid central part terminated with plane ends. Seismic force is considered by sesmic intensity. The program developed in this study is compared with the program PCSTABLS. The ratio of three-dimensional minimum factor of safety to two-dimensional case is examined and factor of safety changes are showed for the ratio of cylindroid length to slope height and numbers of slice. On such bases the following conclusions may by made : (1) The program developed in this program is less conservative than the program PCSTABLS. (2) The value of F2 of this study shows the larger differences than that of PCSTABLS with increasing friction angle (3) Factors of safety computed for 3-D geometry differ considerablely from ordinary 2-D factors of safety. Since Fb/F2 exceeds unity, three -dimensional effects tend to increase the factor of safety. (4) As the ratio of three - dimensional failure width of slope height, b/H increase, the value of Fb/Ff decreases and approaches 1.0 when bye is 14. (5) In calculating the factor of safety using the developed program the number of slices is suitable with the ranges of 30-40

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.8
• /
• pp.1067-1074
• /
• 2010

In this study, a loosely coupled fluid-structure interaction (FSI) analysis was conducted for a low-pressure (LP) final-stage rotor blade. Preliminary FSI analyses of a $15^{\circ}$ sweptback wing and a NASA Rotor 37 compressor blade were performed for verifying the boundary conditions. The results were compared with the established literatures for each model. The FSI analysis of the $15^{\circ}$ sweptback wing was carried out under both stable and unstable conditions. The excessive deformation of the wing was observed within 0.05 s under the unstable condition which is higher than the divergence speed of a wing compared with the stable condition. On the basis of the results of a steady-state study, an unsteady state FSI analysis was conducted for a NASA Rotor 37. Different deformations were observed at trailing edge of the blade in the static FSI and dynamic FSI analysis. A 3D FE model of a LP rotor was generated from the span-wise section data. In order to develop a reasonable model, an impact test was performed and compared to the FE model. Using this FE model, the steady-state FSI analysis was performed successfully.

• Journal of Korean Society of Forest Science
• /
• v.101 no.3
• /
• pp.365-373
• /
• 2012

This study purposed to extract and assess the accuracy of assessment for deforestation area in Wonju city using medium resolution satellite image. The total size of deforestation area during the last nine years (2000-2008) was about 467 ha, and it was occurred annually about 52 ha. The most frequent form of deforestation was settlements (72%). Ninety percent of the size of deforestation was less than 2 ha in size. In addition, 79 percent of deforestation area was found within 500 m from the road network and within 100 m of the Forest/Non-forest boundary. This study compared the deforestation based on the administrative information (GIS deforestationI) with the deforestation (RS deforestation) extracted from the satellite imagery by vegetation indices (NDVI, NBR, NDWI). Extraction accuracy, mean-standard deviation${\times}1.5$ applied 3 by 3 filtering, showed reliable accuracy 35.47% k-value 0.20. However, error could be occurred because of the difference of land-use change and land-cover change. The actual rate of land-cover change deforestation area was 32% on administrative information. The 7.52% of forest management activities area was misjudged as deforestation by RS deforestation. Finally, the comparison of land-cover change deforestation (GIS deforestationII) with the RS deforestation accuracy, as a result NDVI mean-standard deviation${\times}2$ applied 3 by 3 filtering, showed improved accuracy 61.23%, k-value 0.23.

• Journal of Korean Society for Geospatial Information Science
• /
• v.16 no.1
• /
• pp.83-93
• /
• 2008

The topographic effect is one of the most important component in the solution of the geodetic boundary value problem (geodetic BVP). Therefore, topographic effect should be considered properly for developing the precise geoid model, especially for the area where contains many mountains like Korea. The selection of gravity reduction method in the context of the precise geoid determination depends on the magnitude of its indirect effect, the smoothness and magnitude of the reduced gravity anomalies, and their related geophysical interpretation. In this study, Korean digital elevation model with 100m resolution was constructed and topographic effect was calculated by three reduction methods as like Helmert condensation method and RTM method and Airy-isostatic reduction method. Through the analysis of computation results, we can find that RTM reduction method is the best optimal method and the results shows that gravity anomaly and indirect effect of geoidal height are $0.660{\pm}13.009mGal$, $-0.004{\pm}0.131m$ respectively and it is the most gentle slow of the three methods. Through this study, it was found that the RTM method is better suitable for calculating topographic effect precisely in context of precise geoid determination in Korea than other reduction methods.

• Economic and Environmental Geology
• /
• v.54 no.1
• /
• pp.117-126
• /
• 2021

Satellite magnetic observations reflect the magnetic properties of deep crust about the depth of Curie isotherm that is a boundary where the magnetic nature of the rocks is disappeared, showing long wavelength anomalies that are not easily detected in near-surface data from airborne and shipborne surveys. For this reason, they are important not only in the analyses on such as plate reconstruction of tectonic boundaries and deep crustal structures, but in the studies of geothermal distribution in Antarctic and Greenland crust, related to global warming issue. It is a conventional method to compute the spherical harmonic coefficients from global coverage of satellite magnetic observations but it should be noted that inclusion of erroneous data from the equator and the poles where magnetic observations are highly disturbed might mislead the global model of the coefficients. Otherwise, the reduced anomaly model can be obtained with less corruption by choosing the area of interest with proper data processing to the area. In this study, I produced a satellite crustal magnetic anomaly map over East Asia (20° ~ 55°N, 108° ~ 150°E) centered on Korean Peninsula, from CHAMP satellite magnetic measurements about mean altitude of 280 km during the last year of the mission, and compared with the one from global crustal magnetic model (MF7). Also, a comparison was made with long wavelength anomalies from EMAG2 model compiled from all near-surface data over the globe.

• Tunnel and Underground Space
• /
• v.31 no.6
• /
• pp.623-646
• /
• 2021

As the demand for electric power increases with acceleration of electrification at home and abroad, the needs for coal-fired electrical power plant are accordingly increased. However, these coal-fired electrical power plants induce also many environmental problems such as increase of air pollutants, increase of possibility of land contamination by reclamation of coal ash, even though these power plants have a good economical efficiency. In case of a by-product of coal-fired electrical power plants, only 70% of them are recycled and the remaining 30% of by-product are fully buried in surrounding ground. Consequently, this study deals with coal ash backfilling mechanism in abandoned mine openings for the purposes of increasing the coal ash recycling rate as well as securing the mine area stability. In order to analyze the backfill and ground reinforcement by interaction between rock mass and backfills, the copying samples of discontinuous surface with different roughnesses were produced for bond strength tests and direct shear tests. And statistical analysis was also conducted to decide the characteristics of bond and shear behavior with joint roughness and their curing day. Numerical simulations were also analyzed for examining the effect of interface behavior on ground stability.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.6C
• /
• pp.321-329
• /
• 2009

Laboratory compressive test was conducted on 6 different types of rock in order to investigate the characteristic of critical strain under uniaxial and triaxial stress condition. The results of uniaxial compressive test mostly ranged within 1~100MPa, the critical strain was also located between 0.1~1.0%. Therefore the results distributed within the upper and lower boundary proposed by Sakurai (1982). And the failure/critical strain ratio (${\varepsilon}_f/{\varepsilon}_0$) showed between 1.0~1.8 value depending on the uniaxial compressive strength. The results of critical strain by triaxial compressive test showed below 0.8% value for all test, the M value calculated from uniaxial and triaxial compressive test results ranged 1.0~8.0 for most of rock specimens. It is concluded that failure strain (${\varepsilon}_{f3}$) of rock mass, which is in triaxial stress condition is larger than the results of uniaxial stress condition (${\varepsilon}_{f1}$) by 1.0~8.0 times and value showed 1.0~1.8 larger value than critical strain (${\varepsilon}_{01}$). Therefore it is a conservative way for rock tunnel to use critical strain (${\varepsilon}_{01}$) calculated from a uniaxial compressive strength on tunnel displacement monitoring.

• The Journal of Korean Academy of Prosthodontics
• /
• v.61 no.3
• /
• pp.234-244
• /
• 2023

Tooth wear refers to the loss of dental hard tissue caused by various physiological and pathological causes, and excessive pathological wear can cause complications such as pathological changes in dimensions, occlusal disharmony, loss of function, and aesthetic problems. The cause of tooth wear can be caused by attrition, abrasion, corrosion and abfraction, and it is known to act in a multifactorial etiology in interocclusal activity. In patients with excessive pathological wear, it is important to determine whether or not the vertical dimension of occlusion is reduced, and complete oral rehabilitation should be achieved with the adaptation of the neuromuscular and temporomandibular joint through accurate diagnosis and analysis. The patient in this case was a 63-year-old male patient, who presented discomfort to cold beverage due to severe tooth wear. After analysis of the patient's vertical dimension of occlusion, a full mouth rehabilitation was performed with increasing vertical dimension of occlusion. The goal of treatment was to improve the occlusal plane with the equal-intensity contact of all teeth, harmonious anterior guidance and immediate disclusion of all posterior contacts. After rehabilitation, the patient was satisfied with function and esthetic appearance.

• Journal of the Korean Arthroscopy Society
• /
• v.13 no.1
• /
• pp.14-21
• /
• 2009

Purpose: To investigate MRI findings of the repaired anterior cruciate ligament (ACL). Materials and Methods: Seventeen of arthroscopic ACL primary repair with sutures pull-out technique were followed for 21.4 months (range: 12 to 60 months). Stability was assessed with physical examination and KT-1000 arthrometer (MED metric, San Diego, CA) and postoperative MRI checked with time. The patients were divided into 2 groups according to the location of tear which was defined with the location of remained synovial sleeve. Group I (11 patients) comprised that the tear was located within proximal 1/3 of ACL substance and group II (6 patients) comprised below proximal 1/3. MRI findings of the repaired ACL were evaluated by its course, sharpness, thickness and signal intensity using 3 grade system and correlated with its location of tear. Results: In all cases, Lachman test and flexion-rotation drawer test were negative, pivot-shift test was less than grade 1 and the mean side-to-side difference by use of KT-1000 arthrometer was 1.4 mm (range: -1.0 to 2.5 mm). The overall continuity of the repaired ACL was well maintained in all cases. However, mild sagging was observed in 10 cases(58.8%), mild obscure contour in 6 cases (35.3%), increased thickness in 8 cases (47.1%) and slight increased signal intensity in 5 cases (29.5%). There was no statistical significance in all parameters between 2 groups. And a focal defect at the femoral attachment site in sagittal image was observed in 7 cases (41.2%) of all patients which comprised 2 cases (18.2%) of group I and 5 cases (83.3%) of group II. It was observed more frequently in group II with statistical significance (p=0.035). Conclusion: Some abnormal MRI findings such as mild sagged course, obscure contour, increased thickness and signal intensity, the focal defect at femoral attachment site could be observed even though the stability was well maintained clinically. We thought that the focal defect was affected by the location of tear of ACL.

• Proceedings of the KSR Conference
• /
• 2007.11a
• /
• pp.1379-1385
• /
• 2007

In domestic transitional zone design, there is regulation to prevent generation of irregular substructure behaviors that negatively influence in prevention of plasticity settlement on approach section and contact section as well as relieve overall track rigidity by reducing sectional foundation and track stiffness difference, but design guideline that considers dynamic behavior of transitional track in actual service line is very insignificant. Therefore in this study, characteristics of transitional track dynamic behaviors by substructure stiffness are researched and measured dynamic response of transitional track by substructure stiffness in order to prove correlation between substructure and track and calculate elasticity(stiffness) and track load of transitional track by using measurement and formula to provide basic information for developing design guideline considering dynamic behavior of service line transitional track.